Almost three million people have fled Syria's bloody civil war. UN figures show the human tide began in earnest in early 2012.

Experts say the latest numbers are not surprising, after relatively low levels of migration in the early months of 2013.

"The main route through Libya was closed for so long that people in sub-Saharan countries have been waiting for a couple of years," says Franck Duvell, associate professor at the Centre on Migration, Policy, and Society at the University of Oxford.

"So the numbers have been building up and people were waiting for the very first opportunity to move," he says.

"I'm not sure this implies that we are going to see ever-more people arriving in the EU over the next couple of months. We've got to wait and see."

Much depends on the chaotic political and security situation in Libya, where a BBC team has recently seen evidence that large numbers of migrants are still waiting to cross. Some estimates put the figure as high as 300,000.

Italy complains that since last October, when it launched its "Mare Nostrum" [Our Sea] rescue operation, the cost of patrolling its patch of the Mediterranean has risen to 300,000 euros (£240,200: $408,000) a day.